Well scratcher



1 Claim. (Cl. 166173) "This invention relates to the drilling and completion of wells by the rotary method and is directed to improvements in devices for improving the quality of cementing operations for cementing well casing within the bore hole. The invention finds particular usefulness as applied to devices known in the art as well scratchers. Such devices are mounted on the outer surface of the casing and are provided with scratcher wires for engaging the wall of the bore wall to remove drilling mud and filter cake and to cause turbulence in the liquid mud column in order to improve the action of the cement in displacing the liquid mud, gel and filter cake from the annulus around the casing.

The present invention is concerned with improvements in the mounting of the scratcher wires on the carrier strip which is attached to the casing. This mounting of the scratcher wires should afford the wires maximum freedom of movement without danger of fracturing or exceeding the elastic limit of the material, and without reducing their elficiency in operation. Furthermore, the scratcher wire mounting must be capable of withstanding very severe usage and abuse since the casing sections with the scratcher assemblies attached are customarily stored on horizontal racks and thus subjected to crushing contact with adjacent casing sections. The requirement for flexibility may be met by providing wire coils at, or near the juncture of the scratcher wires, but these coils must be protected against damage by contact with other casing sections on the horizontal storage rack.

In accordance with this invention, we provide an improved mounting for scratcher wire assemblies which includes means for protecting the spring coil parts from damage and which mounting is particularly adapted for economical manufacture on a quantity basis.

Other objects and advantages will appear hereinafter.

In the drawings:

Figure 1 is a side elevation showing a preferred embodiment of our invention.

Figure 2 is an enlarged view showing details of the mounting of one of the scratcher wire assemblies.

Figure 3 is a sectional plan view taken substantially on the lines 3-3 as shown in Figure 2.

Figure 4 is a sectional view taken substantially on the lines 4-4 as shown in Figure 2.

Referring to the drawings.

The scratcher device embodying our invention includes a carrier strip which may be mounted on the outer surface of a casing section 11 and fixed in place by any convenient means, such as for example, tack welding 12. The carrier strip 10 supports a plurality of scratcher wire assemblies 13. Each of these assemblies 13 is formed from a single length of wire terminating in upturned ends 14 and 15. The scratcher wire 16 which carries the upturned end 14 may be somewhat longer than its companion wire 17 which carries the upturned end 15. The scratcher wire 16 projects from one end of a spring coil 18 having an axis which extends substantially radially with respect to the casing 11. Similarly the scratcher wire 17 projects from one end of a spring coil 19 The coils are connected by means of a mounting section ori offset footpiece 20 which rests on the upper surface of the carrier strip 10.

In order to provide clearance adjacent the coils 18 and- 19, apertures 21 and 22 are formed in the carrier strip 10. These apertures permit the spring coils to twist with respectto the ofifset footpiece 20, in order to accommm date movement of the wire ends 14 and 15 in any direc-- tion. The presence of the apertures permits the coils to rock or twist in a manner which would not be possible{ if the coils rested on the outer surface of the carrier strip. The apertures 21 and 22 are formed by punching out a section of the material of the carrier strip 10 and by bending or folding back an additional portion to form the protecting rib 23. The protecting rib is V-shaped in cross section and has one end joined integrally to the carrier strip. The other end 24 is free and unsupported and terminates flush with the inner surface 25 of the carrier strip 10 so that it rests against the outer surface of the casing 11 when the carrier strip is installed in place. The apex of the V of the rib 23 is relatively close to the spring coil to afford protection for the latter against crushing contact with adjacent casing sections on the horizontal rack. Furthermore, the rib 23 protects the adjacent spring coil against damage by contact with objects in the well bore.

Each scratcher wire assembly 13 is held in place on the carrier strip by means of retainer fingers 26 which are cut from the carrier strip 10 and then bent back toward initial position to clamp the footpiece section 20 in position. The free ends 27 of the retainer fingers are deformed laterally within the slot 28 to secure a positive anchorage. This form of attachment for mounting the scratcher Wire assemblies 13 on the carrier strip 10 serves to anchor the assemblies solidly, and prevents separation of the parts in service or in rough handling prior to installation in the well bore.

The retainer fingers 26 and the ribs 23 are designed so that they may be formed by punch press operations using multiple stage dies.

In use, the carrier strip 10 with the scratcher wire assemblies 13 in place, are secured to the casing sections by tack welding 12. The casing sections are lowered into the well bore in the conventional manner. The casing string made up of the individual casing sections is rotated from the surface to cause the laterally extending scratcher wires to abrade the well bore and to remove gel and filter cake. The rotary motion of the casing causes the scratcher wires to induce turbulence in the mud column outside the casing and thereby promote more efiicient displacement of the liquid mud, gel and filter cake, from the annulus by the cement grout, during the cementing operation. The fact that the scratcher wires 16 and 17 are of different lengths and each in contact with the well bore, causes them to assume different angular positions within the Well bore thereby contributing to their ability to create turbulence when the casing 11 is rotated, or reciprocated.

The above described mounting for the scratcher wire assemblies is effective to prevent the scratcher wires from being dislodged from the carrier strip 10 even though the casing 11 should hang oficenter in the well. The spring coil mounting for the scratcher wires is protected from damaging lateral contact by means of the outwardly projecting ends 23.

Having fully described our invention it is to be understood that we do not wish to be limited to the details herein set forth, but our invention is of the full scope of the appended claim.

We claim:

In a well scratcher device adapted to be fixed upon.

thcbuter surface of a well pipe, the combination of: a carrier strip having a wall of uniform thickness and transversely curved to contact the outer surface of the Well pipe, 21 scratcher wire assembly including a helical spring coil having a scrateher wire projecting laterally from one end and a. foot piece mounting section extend ing from the other end, means for fixing the toot piece mounting section upon the outer surface of the carrier strip to position the axis of the helical spring coil substantially normal thereto, a protecting rib positioned adjacent the helical spring coil and having a central portion projecting outward from the carrier str-ip to protect the helical spring coil from contact with the well bore, said rib being cut from the wall of the carrier strip and displaced laterally to provide a clearance opening in the.

carrier strip adjacent said helical spring coil, the clearance opening vPermitting unobstructed rocking movement of the helical spring coil, one end of the rib remaining being free and extending in a generally radial direction into the clearance opening, the extreme tip of the free end of the rib being flush with the inner surface of the carrier strip for supporting contact with the outer surface of the well pipe.

References Cited in the file Of this patent UNITED STATES PATENTS 2,412,876 Edwards Dec. 17, 1946 2,506,405 Wright May 2, 1950 2,671,515 Hall Mar. 9, 1954 2,751,015 Baker V June 19, 1956 FOREIGN PATENTS 725,866 Great Britain Mar. 9, 1955 

